Anticorrosion packing assembly



UTE ST AN TICORRO SION PACKING ASSEMBLY Ralph T. Halstead, Somerville,N. J assignor to Johns-Manville Corporation, New York, N. Y., acorporation of New York No Drawing. Application July 10, 1934, SerialNo. 734,527

4 Claims. (Cl. 1067.6)

This invention relates to an anticorrosion packagent with the asbestosfibres, forming a large ing assembly, particularly to packing materialpart of the packing material. Thus, the wateradapted for use therein,and to an anticorrosion soluble anticorrosion agent may be formed intofriction material. an aqueous solution and impregnated into asbes- 5';In an assembly comprising packing or friction tos fibres before thelatter are lubricated. For 5 material, Water and a metal memberconstituted example, strands of loose asbestos yarn or roving ofcorrodible material of the type of iron, cormay be fabricated into thebase material for the rosion frequently occurs at a rate that is verypacking, as by being braided in conventional undesirable. For example,valves having stems manner. The fabricated material is then imof ironpacked with certain asbestos compositions mersed in or impregnated by anaqueous solu- 10 have been found to undergo rapid corrosion when tion ofthe anticorrosion agent, the impregnated wetted with water and thenallowed to stand in material is subjected to drying, suitably at ancontact with air. elevated temperature, to remove the water, and

It is a purpose of the present invention to prolubricant consisting of aviscous plastic mixture vide an anticorrosion packing or frictionmaterial of graphite or graphite mixed with a lubricating 15 that may bedisposed in contact with a member oil or grease, for instance, is forcedby pressure of the type of an iron valve stem and in the into thepreviously impregnated fabricated base. presence of moisture and air,with minimization The amount of anticorrosion agent required or completeelimination of the corrosion of the is relatively small. Thus, there maybe used an member for a substantial period of time. Other amount ofanticorrosion agent corresponding apobjects and advantages of theinvention will approximately to 2 to 10 parts by weight for 100 pearfrom the description that follows. parts of fabricated fibrous basematerial.

The invention will be particularly illustrated It has been found thatwhen a packing so by the description of an assembly including packmadeis used in contact with a metal member ing and a member constituted ofiron as the corconstituted of a corrodible material of the type rodiblematerial, the term iron being used to of iron and in the presence ofwater, corrosion of include steel. the said member is practicallyeliminated, even I have found that the rate of corrosion of an thoughair has access to the wet packed assembly. iron valve stem in contactwith water and pack- Once the surprising result has been obtained 3 ingmaterial, such as lubricated asbestos fibres, various theories orexplanations may be admay be greatly reduced by the intimate assovancedto account for the result. ciation with the packing material of acompound While it is understood that the present invenselected from thefollowing group: a secondary tion is not limited to any theory orexplanation, sodium hydrogen phosphate, tertiary sodium the followingcomments are made as representphosphate, potassium chromate, potassiumdiing largely the explanation of the mechanism of 35 chromate, sodiumbicarbonate, sodium carbonate, reduction of the rate of corrosion.Material of and sodium tetraborate. The compounds includthe type ofiron, as the term is used herein, is a ing sodium or potassium areillustrative of the material that is corrodible in the presence ofcorresponding salts of the less expensive alkali water and air and, whenimmersed in water,

40 metals in general, which may be used instead of tends to dissolve atits superficial portion, to a 40 the particular ones enumerated above.While slight extent at least, to produce ions which have particularlygood results have been obtained with a positive charge and leave theundissolved mathe sodium and potassium salts of the acid raditerialelectronegatively charged. This condition y cals listed, there may beused similar compounds prevails, also, when the iron is present as oneof that are equivalent for the present purpose. the elements of agalvanic couple, packing ma- 45 If the minimized corrosion is desiredfor a temterial of the type described constituting the other poraryperiod only, the agent associated with the element and water serving asthe connecting packing may be sodium silicate, primary sodium medium.But, when an anticorrosion agent, of phosphate, lead chromate, or leadacetate, for the type described, is associated with the packexample. Itwill be understood, however, that ing material in the galvanic couple,there is a 5 agents giving the more permanent anticorrosion decrease inthe electronegative charge on the properties are preferred. said metalmember or actually reversion of the 3 i The method of making theanticorrosion packpolarity of the couple. Thus, the packing now ingmember involves the impregnation or otherbecomes electronegative withrespect to the metal wise intimate association of the anticorrosionmember. This effect occurs when the concen- 55 tration of anticorrosionagent in the aqueous medium bathing the packing and themetal member isvery low. Thus, a concentration of 2.5 parts of trisodium phosphate(expressed as Na3PO4.12H2O) present in parts by Weight of the aqueousbathing medium has been found adequate to reverse the polarity.

The quantitative efiect of the presence of an anticorrosion agent uponthe electrode potentials of a steel member, water, and a packingmaterial in contacting relationship, is illustrated by the followingdata. With no anticorrosion agent present in the packing, and with waterconstituting the medium in the galvanic couple, the packing materialhada potential of plus millivolts and the steel had a negative potentialof 498 millivolts, thus making the packing material electropositive withrespect to the steel rod by 683 millivolts. When trisodium phosphate inincreasing amounts was associated with the packing material, asdescribed above, the electronegativity of the packing, with respect tothe steel, was augmented until finally the sign of the potentialdifference was actually reversed. Thus, when the aqueous medium wassaturated with trisodium phosphate, the packing material showed anelectrode potential of minus 154 millivolts and the steel rod showed anelectrode potential of plus 214 millivolts, thus making the packingmaterial electronegative with respect to the steel rod by 368millivolts. It will be understood that the electrode potential of eachelement, stated separately, represents the potential diiference from theaqueous medium taken as of zero potential.

In applying the lubricant to the fabricated base material impregnatedwith the anticorrosion agent, the lubricant tends to seal theanticorrosion agent within the packing and thereby reduce the rate atwhich the anticorrosion agent may be leached from the packing by watercoming in contact with the packing during the use thereof.

When, for example, anticorrosion friction material is to be made,asbestos fibres may be impregnated with an anticorrosion agent asdescribed, the fibres, either with or without being first fabricatedinto a base material, then associated with a rubber or otherconventional friction compound in a usual manner, and the frictioncompound then hardened.

The details that have been given are for the purpose of illustration,not restriction, and variation therefrom may be made within the scope ofthe appended claims.

What I claim is:

1. A packing member, for use in contact with a metal member constitutedof corrodible material of the type of iron and in the presence of water,comprising packing material including a lubricated asbestos fibrecomposition and. an agent associated therewith and adapted to increasethe electronegativity of the packing material with respect to the water.

2. A packing member, for use in contact with a metal member constitutedof corrodible material of the 'type of iron and in the presence ofwater, comprising packing material including a lubricated asbestos fibrecomposition and an agent associated therewith and selected from a groupconsisting of the following: a secondary or tertiary alkali metalphosphate, an alkali metal bicarbonate or carbonate, and anlalkali metaltetraborate.

3. An article of manufacture, for use incontact with a metal memberconstituted of corrodible material of the type of iron and in thepresence of water, comprising asbestos fibres, a water-solubleanticorrosion agentassociated with the saidfibres, and a water-insolublematerial disposed over the said agent and reducing the rate of leachingout by water.

4. A packing member, for use in contact with water and a corrodiblematerial of the type of iron, comprising asbestos fibres, aWater-soluble compound impregnated into the fibres and adapted to makethe packing member electronegative with respect to water, and awater-insoluble material disposed over the impregnated fibres, the

proportion of the said compound being approximately 2 to 10 parts byweight for 100 parts of the fibres.

' RALPH T. HALSTEAD.

